A METHOD AND A SYSTEM FOR EXPLOITATION OF GAS FROM WASTE DISPOSAL SITES

Abstract: A method and a system for exploitation of gas from waste disposal sites is described, that is biogas being generated during anaerob decomposition of the waste deposited on the disposal site, and where the gas is recovered through a recovering system consisting of a number of drillings (10) and via MPR-module (measuring pump and adjusting module) is lead to boiler or gas engine-driven generator with transformer for sale of produced energy as electricity to the electricity company and heat to heating consumers, where the gas from each single drilling (10) is lead to the MPR-module through separate tubes, that the per cent content of methane (CH4) and oxygen (O2) in the gas and the gas quantity from each drilling (10) currently is measured and adjusted by means of a common measuring and adjusting equipment, whereto gas from each single drilling (10) in turn is lead, and that the O2-concentration in the gas continuously is measured on the suction side between the absorption manifold (12) and the compressor (34), for instance screw compressor.

Description: Λ method and a system for exploitation of gas from waste disposal sites The present invention relates to a method for exploitation of gas from waste disposal sites, that is bio gas being generated during anaerob decomposition of the waste deposited on the disposal site, and where the gas is extracted through an extracting system comprising a number of drillings and via a MPR-module (Measuring Pump and Regulating module) is lead to a boiler or a gas engine-driven generator with transfor¬ mer for sale of the produced energy as electricity to the electricity company and as heat to heat consumers. By depositing waste on disposal sites, for instance so-called controlled disposal site with bottom-membrane etc., a micro biological conversion of the waste - first during an aerob decomposition, where the present oxygen is consumed - thereafter during anaerob decomposition where the biogas is generated. When the disposal site has reached a stable anaerob phase, the produced gas will maintain 30 - 60 % methane; and the gas may be exploited for purposes of energy supply. A number of systems for exploitation of gas from disposal sites are known, and the largest systems are producing more than 200,000 m3 disposal site gas per day, which corresponds to an equivalent quantity of oil of about 100 tonne per day. The invention has for its purpose to provide an improved method for exploitation of gas from waste disposal sites, and which makes it possible to obtain an optimum and secure operation for instance by means of a standardized MPR-module. The method according to the invention is distinctive in that the gas from each drilling is lead to the MPR-module through individual pipes, that the per cent contents of methane (CH4) and oxygen (O2) in the gas and the gas quantity from each drilling currently is measured and controlled by means of a common measuring and controlling equipment, whereto gas from each drilling in turn is lead, and that the O2-concentration in the gas continuously is measured on the suction side between the suction manifold and the com¬ pressor. By means of simple provisions it hereby becomes possible to obtain an optimum and securely controlled production of gas, where the quality of the gas from each drilling currently is controlled. The per cent contents of methane in the gas (optimum calorific value) respectively contents of oxygen (for the sake of the security) continuously are measured and registered. To avoid danger of explosion continuous measuring and regi¬ stering of the concentration of oxygen on the suction side of the system is also measured - just in front of the compressor. Appropriately extraction drillings are used which each consists of two tubes and a gravel filter, that one of the tubes, the gas extracting tube, is perforated or provided with slits, while the other tube, the emptying tube, is adapted to receive a diving pump, if the liquid level in the disposal site becomes too high and covers the suction filter of the gas extracting tube. The humid and hot gas from the drillings is lead to the MPR-module through subter¬ ranean pipelines, which advantageously are inclined towards the drillings, so that the condensed water automatically runs back to the drillings. Furthermore eventual condensed water being collected in pockets of the subterranean pipelines are blowed back into the drillings by means of a return-blowing system of the MPR-module. Even if the pipelines are placed inclined towards the drillings, difference settings on the disposal site - in consequence of different conversion of the waste - may cause pockets in the pipelines. The invention furthermore relates to a system for use by the exploitation of gas from disposal sites (bio gas) according th the invention, which system is distinctive in that the MPR-module is constructed in a standard container, which is divided into a control room and a pumping room provided with a measuring and regulating string unit for each drilling, for instance 40 string units, each being connected to a suction manifold, and which comprises a flow-meter, a motor valve, a side pipe stub with a magnet valve and closing valves. Appropriately the system according to the invention is such provided that each measuring and regulating string unit by means of said side pipe stub with magnet valve is adapted in turn to be connected with a common measuring equipment with a methane-meter and an oxygen-meter. Furthermore the system is such provided that each pipeline between measuring and re¬ gulating string unit and drilling by means of said closing valves may be connected to the pressure side of a compressor if needed in order to blow water return, which is col¬ lected in the pipeline, to the drilling. The invention is explained in more detail in the following with reference to the drawing, in which :- Fig. 1 shows a preferred embodiment for gas an extraction drilling for use by the method and system according to the invention, Fig. 2 shows a vertical cross section through the MPR-module (pumping room) in the container - seen towards the suction pipe arrangement, Fig. 3 shows a vertical cross section through the MPR-module (pumping room) in the container - seen towards the cooling system (to the right), Fig. 4 shows a vertical longitudinal section through the MPR-module (pumping room) in the container - seen towards pressure and cooling system, Fig. 5 shows a vertical longitudinal section through the MPR-module (pumping room) in the container - seen towards the battery of measuring and regulating strings for gas extraction drillings, Fig. 6 shows a sectional view of measuring and regulating string for gas extraction drilling, and Fig. 7 shows a partial vertical longitudinal section through the control room of the MPR-module. The drilling 10 shown in Fig. 1 , of which there ought to be up to about 6 drillings per ha. on a disposal site, is a double-drilling with two plastic pipes, namely a perforated gas extraction tube 38 and a slited emptying tube 40, both being surrounded by a suction filter 36 of filter gravel. Upwardly the drilling 10 is tightened against entry of atmospheric air by means of clay 42. The gas extraction tube 38 is by means of a subterranean pipeline 32 connected with a MPR-module (Measuring Pump and Regulating module). At the top the drilling 10 is provided with a service well 44, through which for instance a diving pump may be lowered into the emptying tube 40, if the water level in the disposal site rises to a level over the suction filter 36. Each of the pipelines 32 from each of the drillings 10 are lead to a centrally placed MPR-module, which is constructed in a standard container 2 and comprises a control room 4 (Fig. 7) and a pumping room 6 (Figs. 2 - 5). Control room 4 and pumping room 6 are separated gastight among others by means of an interior wall 46 with an inspection window 48 (Fig. 2). The pipelines 32 are lead into the MPR-module via an oblong inlet box 50 at a long side wall 52 with a long narrow inlet opening 54. Along the long side wall 52 a number of 40 similar measuring and regulating strings 8 (Figs. 5 and 6) are arranged, which all are connected to a common suction manifold 12, and which all comprise a flow-meter 14, an axial compensator 16, an engine-operated regulating valve 18, a side pipe stub 20 with a magnet valve 22 and two closing valves 24 (butterfly valves), so that each measuring and regulating string in order either to current control of oxygen and methane concentration of the gas from each drilling 10 by being connected to a pump 70 for a common measuring equipment 26 (methane-meter 28 and oxygen-meter 30) or to blow water in the pipelines 32 return to the respective drillings by exercising pressure by establishing connection to the pressure side of the compressor 34 (screw compressor - Fig. 4) via return blowing pipes 56. From the suction manifold 12 the gas is lead via a suction tube 58, a gas filter 60, a valve 62, a flame filter 64, and f rther an oxygen-meter 68 to the suction side of the screw compressor 34, as the system is closed down, if the concentration of oxygen exceeds 3.5% corresponding to 20% of the upper limit of explosion. Before the gas leaves the MPR-module through a transmission pipeline 66 to the gas engine and/or the gas broiler, respectively, the gas passes through different filters, a cooling system - cooling water and oil separator, etc. The gas is cooled to a dew point of about 2° C to avoid condensat in the transmission pipeline 66 and also to make the gas less aggressive to the engine. In practice the continuous control measuring of the gas is exercised from each of the 40 measuring and regulating strings 8, by the fact that gas from each string 8 via the side pipe stub 20 and the magnet valve 22 in turn is lead to the common measuring equipment 26 in order to determine the contents of methane and oxygen in the gas from the respective drillings 10. By means of the pump 70 the gas is sucked from a string 8 past the methane-meter 28 and the oxygen-meter 30 directly to the suction manifold 12 a certain time - until the quality of the gas stream lead past the common measuring equipment with certainty is equivalent to the gas quality from the specific string 8 or drilling 10. In this manner control measuring and registration of the gas from each drilling may be carried out with a time interval of about 1 hour. In the control room 4 a computer is placed, which on background of the measurings controls the opening and closing function of the engine-operated regulating valves 18 on the strings 8 for the respective drillings 10. In the computer the optimum percentage of methane and of oxygen may be determined for each drilling 10. For instance the percentage of methane may be estimated to 45%. Hereafter the computer will open the individual string 8, respectively the drilling 10, if the percentage of methane exceeds 45 % and close if the percentage of methane drops under 45 % . The frequent measurings result in the fact that the system at any time may be regulated in accordance with the actual changes in the conditions of production, so that the optimum gas quantity (energy quantity) at any time is extracted. Furthermore the upper limit value for the percentage of oxygen may for instance be estimated to 1 %, so that the computer closes for the individual string 8 respectively drilling 10, if the percentage of oxygen exceeds this limit value. Hereby it is avoided, that atmospheric air is sucked down into the drilling, that is that it may be avoided killing the gas producing anaerob bacteria.

Claims: CLAIMS: 1. A method for exploitation of gas from waste disposal sites, that is biogas being generated during anaerob decomposition of the waste deposited in the disposal site, and where the gas is extracted through an extraction system comprising a number of drillings (10) and via a MPR-module (Measuring Pump and Regulating module) is lead to a boiler or a gas engine-driven generator with transformer for sale of the produced energy as electricity to an electricity company, characterized in that the gas from each drilling (10) is lead to the MPR-module through individual pipes, that the per cent contents of methane (CH 4 ) and oxygen (O2) in the gas and the gas quantity from each drilling (10) currently is measured and controlled by means of a common measuring and controlling equipment, whereto gas from each drilling (10) in turn is lead, and that the O2-concentration in the gas continuously is measured on the suction side between the suction manifold (12) and the compressor (34). 2. A method according to claim ^characterized in that drillings (10) are used, which each consists of two tubes and a gravel filter (36), that one of the tubes, the gas extracting tube (38), is perforated or provided with slits, while the other tube, the emptying tube (40), is adapted to receive a diving pump, if the liquid level in the disposal site becomes too high and covers the suction filter (36) of the gas extracting tube (38). 3. A method according to claim 1, characterized in that the humid and hot gas from the drillings (10) is lead to the MPR-module through subterranean pipelines (32) being inclined towards the drillings (10), and that the condensed water being collected in pockets of the pipelines (32) may be blowed back into the drillings (10) by means of a particular return-blowing system of the MPR-module. 4. A system for exploitation of gas from waste disposal sites, that is biogas being generated during anaerob decomposition of the waste deposited on the disposal site, and where the gas is extracted through a extracting system comprising a number of drillings (10) and via a MPR-module (Measuring Pump and Regulating module) is lead to a boiler or a gas engine-driven generator with transformer for sale of the produced energy as electricity to the electricity company and as heat to heat consumers, c h a - racterizedin that the MPR-module is constructed in a standard container (2), which is divided into a control room (4) and a pumping room (6) provided with a mea- suring and regulating string unit (8) for each drilling (10), for instance 40 string units each being connected to a suction manifold (12), and which comprises a flow- meter (14), a motor valve (16, 18), a side pipe stub (20) with a magnet valve (22) and closing valves (24). 5. A system according to claim 4, characterized in that each measuring and regulating string unit (8) by means of said side pipe stub (20) with magnet valve (22) is adapted in turn to be connected with a common measuring equipment (26) with a me¬ thane-meter (28) and an oxygen-meter (30). 6. A system according to claim 4 and 5, characterized in that each pipeline (32) between measuring and regulating string unit (8) and drilling (10) by means of said closing valves (24) may be connected to the pressure side of a compressor (34) if needed in order to blow water return, which is collected in the pipeline (32), to the drilling (10).

Inventors: JOERGENSEN THOMAS, WILLUMSEN HANS CHRISTIAN, JOERGENSEN, THOMAS, WILLUMSEN, HANS, CHRISTIAN
Applicants: HEDESELSKABET, JOERGENSEN THOMAS, PEDERSEN AS MARIUS, WILLUMSEN HANS CHRISTIAN, A/S MARIUS PEDERSEN, JOERGENSEN, THOMAS, WILLUMSEN, HANS, CHRISTIAN
Application year: 1994
Main classification: B09B1
IPC codes: B09B1, C12M1, E21B43, G01N33